In the field of radioactive waste management the concrete structures are expected to undergo significant heating due to the waste thermal power and significant drying (in the French design, the temperature is not expected to exceed 80°C). The durability assessment of such structures thus requires the knowledge of the evolution of the water vapour sorption properties versus temperature. The latter can be easily estimated using the Clausius-Clapeyron (CC) equation: the approach presented hereafter requires the knowledge of the isosteric heat of adsorption and one desorption isotherm (at ambient or any other temperature). Moreover, it is shown that using the CC equation and the desorption isotherms at two different temperatures, it is possible to estimate accurately the desorption isotherm at any other temperature.